This is the 100th most frequent Polish word.
policji
"Policji" means "of the police" in English.
The word 'policji' acts as a genitive case object indicating possession, belonging to the police.
Byłam na komisariacie policji, aby zgłosić kradzież.
I was at the police station to report a theft.
The word 'policji' here is in the genitive case, used to specify the car is owned or associated with the police.
Widziałem samochód policji jadący w kierunku miasta.
I saw a police car heading towards the city.
Here, 'policji' is used in the genitive case after the preposition 'bać się', which governs the genitive case in Polish grammar.